1. Field of the Invention
The present invention relates to an abnormality diagnosing apparatus for a vehicle that diagnoses the presence or absence of an abnormality in a specific component or system mounted on the vehicle.
2. Description of the Related Art
Generally, in order to improve vehicle reliability, today's computerized vehicles perform abnormality diagnoses of various kinds including, for example, a catalyst deterioration diagnosis for diagnosing the presence or absence of deterioration in a catalyst for purifying an exhaust gas, an evaporative gas leakage diagnosis for diagnosing the presence or absence of leakage in an evaporative gas purge system for purging (releasing) an evaporative gas (fuel evaporative emission) from inside the fuel tank to an intake system, etc. These abnormality diagnoses are performed under a pre-set, particular abnormality diagnosing condition (performance condition, diagnosing method, and judging condition) so as not to adversely affect the drivability, exhaust emission, etc.
However, use environments, driving methods, and running patterns of the vehicle vary from user to user. Therefore, when the abnormality diagnosis is performed under the pre-set particular abnormality diagnosing condition (performance condition, diagnosing method, and judging condition) by a conventional abnormality diagnosing apparatus as described above, the abnormality diagnosis may be performed less frequently (or the abnormality diagnosis may be started, but aborted more frequently before it has been completed) depending on the use environments, driving method, and running pattern of the vehicle. This potentially reduces the performance frequency of the abnormality diagnosis to an extremely low level. For this reason, should an abnormality occur, the abnormality diagnosing apparatus may fail to detect the abnormality at an early stage.